The lack of a Soviet invasion would allow the Poles to withdraw to the Romanian bridgehead where they hoped to hold out until Spring whilst the promised French offensive crushed Germany in the west. Obviously that invasion wasn't coming, which more or less dooms the Poles eventually but it might, ironically, save France. That relies on the Poles pulling off an organised retreat however, which would be unlikely in the chaos of Fall Weiss, it's more likely they'd put up a trademark stubborn and heroic last stand against the Germans but I doubt they could hold much longer than early November.